Automatic switching system



- Sept. 14, 1943. B. D. wlLLls. 253295234 AUTOMATIC SWITCHING SYSTEM Filed Feb. 10,-1941 '5 Sheets-Sheet 2 '1 I I. I a I I I I I I I Q I I I II I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 'II I I I I I I I I I I I I I I I I 4 I I I I I a I I I I I I I I I I I Ig lIIII/IIIIIIIIIIIIIIII! rIIIlI'IllIIl/IIIIIIII rlllllllliulllrliil,nl

v INVENTQR. Ber/Lard D. ZWZ'ZUS WE I W Sept. 14, 1943. B. D. WILLIS2,329,234

AUTOMATIC SWITCHING SYSTEM Filed Feb. 10, 1941 5 Sheets-Shet s INYENTOR. fie/warn. E ZZQ 56 no BY W Sept. 14, 1943.

a B. D. WILLIS AUTOMATIC SWITCHING SYSTEM Filed Feb. 10, 1941 5Sheets-Sheet 4 5-60 INVENT OR. Ber/Lard D. ZWZZZS Sept. 14, 1943. B. D.WILLIS AUTOMATIC SWITCHING SYSTEM 5 Sheets-Sheet 5 Filed Feb. 10, 1941INYFNTOR Patented Sept. r54; 19'4'3' ITED. P N OFF- CE v i 2,329,234 v v:AUTOMATIC SWITCHIINGSYSTEM Bernard 1). Willis, oak Park illlii Wm;Walteri Owen, executor'of said Bernard D; Willis,de-

ceased, assignor to Automatic Electric Laboratories, Inc., Chicago,111., a corporation of Delaware Application February 10, 1941, SerialNo.378,151 u The present invention relatesin generalvto automatic switchingsystems, andmore inpartic- 18 Claimsr (Cl. 179 18) ation performed, isthereforef in accordance with ular to suchswitching Systems as includean impulse sender or calling device at a controlstatg tion, alineextending .to a distantswitching sta-' tion or exchange, and; one ormore automatic switches at the'latter point which are selectivelycontrolled over theline by, the calling device at the control station. II

An example of such a switchingsystem is an automatic telephonesystem, inwhich each subscriberjs line is providedwithj a calling device atthesubscribers telephone, and in whichautomatic switches are provided atthe, exchange {or the purposeof establishing telephone connections undersubscriber v controL, For. convenience, therefora the invention is:illustrated and de-. scribed herein .as a simple .form of automatictelephone system. It is not limited to such use,

however, but may be employed in a varietyof situationswhere -it.isdesired to effect selective actionunderremote control.

The main feature; of the invention is the novel principle in accordancewith which the selecting operation is controlled In automatictelephonesystems whichare in common use, the control is, exercised by'thetransmission of a variable series of impulses whichare generated by acalling device. The number of impulses in a series,

depends on the digit in accordance with which the, calling deviceisoperated, and the selecting operation resulting from thei.;tra"nsmission of a series of impulses is in accordance with the numberof impulsesin the series, This principle of operation.requiresabsolutevaccuracyin the registration of a series of impulses and since the.impulses must be transmitted at rather high .speed, and frequently overlines ill adapted to high speed impulse transmission, certaindifiiculties have been encountered which render itymore the beginning ofthe impulse and is stopped at the end thereof. The switch runs atpredeter-' mined speed for the duration of the impulse, and

the extent of its motion, or the" selecting oper- 15 patent to someextentgthat is, itdispenses'with the length'of the-impulsefdn thissystem fof controlthe duration of each impulse is determined by thedigit called, but'is' also-dependentupon; the speed of thecallingidevicepwliich accordingly must becoordinated with the-speed ofthe automatic switches in order to insure accurate, se-

} lection. I The necessary speed relation between the calling device andswitches is not particue larly diificult of; attainment, but .tlusureqiiiremerit nevertheless introduces a diificulty under certaincireumstaneeswmch renders the system less satisfactory than itotherwisewould be.

My improvedsyst em of selective controlresem bles the system disclosedin' my abovementioned the use of a variables'eri'es of impulses.'At'each operation of the calling device a'fixed number of impulses isgenerated." 'Tw o impulses instead of one are generated, however, andalthough these two impulses are of variable length the selectioneffected does not depend directly upon thelength of the impulses,butupon the ratio of thelength ortne first pulsetd that Of-the second.Thus the speed of'thecallingdevice, withiiir'easonable limits, ientirely immaterial. For the digit 1, 'for example, the ratio of, theduration of the first mpm e tothatof the' second may be as'I10 ist o 1.'A. given calling dvice'may operate at such 'a speed that the durationof the first impulse isonefsecond, while the duration of the secondimpulse is onetenth second Another and theratiobetween mewmmpms willbethe. same;

calling device may have a faster speed such that the duration of thefirst imp ulse' is only one-half se'cond, but the duration 'of thesecondimpulse inthis case will oniy'. be'one-twen'tieth' second,

t will be understood that in my improved syj t em the; calling deviceand likewise thelswitchundrl control thereof f must run' atisomeconstant Speed, but the two speeds do not have a fixed relation to eachother and accordingly these re quirements are easily met. vl 'orinstancethe switch may be operated bye. synchronous motor 1 running. oncommercial power, whichhas asubstantially constant frequency. Thecalling device, on theother hand, maybe provided with a speed governor,.of which several reliable .types are known. Since the callingde'vicespeed isnot.

rigidly associatedj the switch. speed, either speed may be varied withinquite wide limits with vout affecting the selection control.

@Ihe practical application ofthe new principle of selection 1 controldescribed in the: foregoing Supported in bearings on the brackets I and40 there is a short shaft. I8. adapted .to be rotated by apinion I5,which is in meshwith the gear wheel I3. The gear ratio'is four to one,from which it follows that the pinion I and shaft I8 arerotatedthreehundred and sixty. degrees, or one. completerotation,;each'..

time a key such as key 7 is operated. This follows. from the fact that"the operation of. a key rotates shaft I2 andgear wheel I3 ninety degreesand fromthefour to one ratio, between gear wheel I3 and pinion I5. Thegear wheel 43 is rotatable on shaft I81 and is connected thereto bymeans of a helical spring |6,.one end.

of which is secured to the shaft I8 and the other end, of whichissecured to a pin IT. This pin is rigidly fixed to the gear wheel 43 andprojects from the side thereof, as shown in Fig. 3. The 1 spring I6 isnormally under tension, tending torotate the gear wheel 43 in aclockwise direction, as seen in Fig. 2,

tothe fact that the pin I1 is held by the hook '51 on the end of arm 56,as shown in Fig. 4. The

arm 56 is rigidly supported on shaft I 4. Since:

the spring I6 is under tension, it also tends to rotate the shaft I8 andpinion, I5 in a counterclockwise direction, but such rotation isprevented by the dog 59, Fig. 2, which engages with the teeth of thegear wheel I3.

The gear wheel 43 is in engagement with a pinion 20, which is fixed onthe shaft I 9, the latter having bearings-in the-bracket I0. On thisshaft there ,ismounted the windfgovernor comprising vanes 2|. Any otherknownform of governor could be used here, such asa centrifugal governor,for example,

The commutator 10 may be of molded insulat ing material and has a rowofcontacts. 6| to 60 and II, embedded therein, as seen in Figs. 3 and. 6.There-is also a ring '|2'of conducting mate-- rial. The commutator maybe secured to the cover 2 by means of screws, as shown in Fig. .6.

The gear wheel 43 carries a pair of brushes24 and 25 whichcooperate:respectively, with the contacts such as 6| and the ring I2.These brushes are supported in brush holders '22 and 23, which areinsulated from the gear wheel, but are conductively connected together.The brush 24 is normally in engagement with contact II, and this contactis therefore normally vcotnnected through the two brushes to ring I2.gear 43 is rotated, the brush 24 leaves contact 1| and engagessuccessively with contacts 00, '69,

etc., which are thus connected successively to ring I2, since brush 25maintains continuous contact with the ring.

The contacts such as II are each provided with a pin or stud such as I3,these pins extending through the commutator and projecting from the backthereof. There is also a pin I4 associated with the ring I2. These pinsenable suit-,- ablecircuit connections to be made to the commutator. I

. The wiring is shown in1Fig, 12, where the calling device is showndiagrammatically and is indicated by the reference character CD. gAs'shown, there are only'two conductors leading in The. shaft I8 isRotation of the gear wheel cannot normally take place, however, due

to the calling device, these conductors being indicated at 202 and 203.These conductors extend through a suitable opening inthe closure memher4 (seeFig. 1), to the rear of the commutator I0, where. conductor,.202;is connected to the ring I2 by means of the pin .14. Conductor 203 isconnectedto contact? by means of its. pin I3.

This pin 13 isalsoconnected to all of the con-.

tact springs such .as 42 yofthe sets .of contact of contact springs arewiredindividuallyto the pins such as I3 which -.are associated with thecommutator contacts ;0| to 60. That is, contact:

spring 4| associated with the first key I corresponding to the digit iswired to contact 0|, the contact spring corresponding to spring 4|butassociated with the digit 2 keyis wired to contact .62, and so on.There being ten keys,; there will be ten conductors connected asdescribed, ,These conductors, together-with the additional conductor forconnecting the contact springs such as 42 with the contact "II, extendfrom the key contact springs by way of the conduit 5| and theextension4' of the closurememher 4 to the rear of the commutator, where they areconnected as described,

Reference may now be made to Figs. '7 to 11,

inclusive, which showa complete switch con structed in accordance withthe invention.

'The various parts of the switch are mounted on a frame which comprisesafiat metal plate |0| andaisecond metal plate I02 which is bent. as shownin Fig, 3 and secured -to plate I0! by means of screws.

The'switch'bank comprises an arcuate-shaped member I04 having on theface thereof aplurality of contact sets such as I05. her, I 04 ispreferably of molded insulating material, with the contacts such as I05embedded therein,'each contact'having a pin which pro jects at the rearof the member I04 for theattachment of a conductor. The bank may,however, be constructed in other ways, as is well knownin the art. A I vThe switch bank is secured to. the frame by means of two brackets meansI07, as seenin Fig. 7. The bracket I06 includes a part'v/hich restsagainst the frame-plate |0I and which is secured to plate l0| by screws,a second part: extending at right, angles, to the first part andparallel .to the plane of the paper, a third part extending forwardperpendicular to the plane of the paper, and a fourth part extendingparallel to the plane of the paper to Which the endof the bank I04issecured by screws. The bracket I01 When the I includes a part secured tothe frame plate I02 by; means of screws and a'forwardly offset part towhich the lower end of the bank is secured by screws.

right angles to form a bearing member N33. The

shafts II 0 and I I extend through bearings inthe.

frame plate IOI and parallel to the frame plate I02, and areprovi-dedwith bearings in the member 103.. These two shafts Support amovable carriage I I2 which, is threaded on the shaft H0 andfwhich isslidable on the shaft I I I. It will be understood that shafts I I0 andIII pass through springs .which are associated with the keys. The,other; contactsprings such'as 4| of these sets.

The mem The end of frame plate I62 is bent forward at:

openingsin the carriage, and that the threaded opening provided for thethreaded shaft H0 shaft I1I'I:.. The: shaft. I l- II is:.adapteditoztmt'atez the. gear; IMv in; any." position oft the; carriage:througlnthezmediumzof"asquare spline: Id a'iwhicliz lies pa-rtlyr in thegroove; MK and partly inza coreresponding: recess in. the gear; tonwhich. it secured loyal-screw I2'II'.

Extendingwertically upwardtirom thescarriaem i-Iszr there isa. shaft or:red: I its which isiagi'dlys' fixedl'to the carriage... The block:Iim'is slldahlei veiitically onltherrodr M62. Ther elis alsoarveltiibali rotatable shaft I H; whichzis ithrieaded inthe hitch: I518?and which has a bearing. in the -carriage L1 7;: The shaft I 'IfI" isro'ta-tedby'means of a bevel geart' ISIS; in mesh with gear IM ancl-suchrotatiomis effective to rai'se the b'lock H 8-} slidingit albng themama" The reference character 'WI indicates-a pivoted wiper or brusharm.At the lefttliiswiper-arm is bent-in au shape forming a-shortsection-I32 which' is p-arallelt'o but offset from the main part 201' ofthewiper arm, as seen clearly in-Fi'g. 8; The" support I 3U isseouredto-the frameplat-e W1 as shown, and is bifurcated; whereby twodawn-- wardiy extending? members I 33 and I3 1 are formed, whichlieon-op-posit'ezsids-of thesecticn 25' I32 of the wiper arm. The pivotpin II'JI" passes through these parts-and afiords a-bearing or pivotabout whicht'he wiper arm I-2 tis rotatabl'e;

-The wiper ar-m- I21 has a" sl'ot I2 1; as clearl'y' shown in'Fig 7'.The pin- I35; Fig: 8; isrigidly fixed to the block I I8'' and projectstfr'rrough'- the slot [22 in the wiper arm: When the carriage I I 2'ismoved'to the right, the pin- I35'siides-a1'ong" the slot I22; andwhen-'the-block H3 slides" vertically on the rod I IS the pin I3 5rot'ates'the wiper" arm'YI'ZI on its pivot I311 The three wipersorbrushesare-imlicated? at I23 I2 5; and I2 5. At the right hand end:the. wiper arm- IZI- includes an offset portion I3I,,t0 whichthereissecured ablock of'insulating mate'- rial I26. The-wipers I-2-3' I2'5*aresecuredto'this. block; as shownclearl'y'in Fig. 9'. l I

The rod I38 extends" diagonally across;- the switch; asshown in- Fig:'7, and is pivor'cedion. frame plate IOI at I39. Thelowertendofthe.rodrests normally against the insulated. support I4 I. The-pivot I39 isalso insulatedjso'thatithe rodjjisr electrically insulated from theframe and other parts ofthe switch: A terminal member I III'iIs,clamped-tothe rodnear thepivotedend thereof andprovides means forattaching a. condhctorl The arrangement for rotating the shafts It!!!" Iand I II- may now" bedescribed; with reference.

particularly to- Figs: 10 and" 11. Briefly stated;- this arrangementcomprises a powerdri'vemroller I61) which is adaptewtfo hebroug'htintoengage-v ment successively with rollers I51 and'I whicii' aremounted onshafts H and I'Iif, respectively.

The roller IE8 is supported'cn a pivoted. armature I51. The armature I?is operated by two electromagnets I53 and I543 the cores of whichareattached to the=plate I145 The latter'is;set' edgewise against the"frame plate". IQI. and is. fastened thereto by-screws. The armature I151lies inaslot in the plateI'M 'and'is'pro-vided'withi apivot I15.The-armatureIS'I includes'anem tension I69; whichfis bifurcaterli as.shown: ii Fig. 11, the extension thus. comprising, the, ave. membersI55I and IE2 whichtarelprovidedl'wi'tli bearings for theshafit L61OILWhlChfihfiI'OllBXiin; is mounted The shaft IE3- isconnected to e.short flexible shaft. IV'M, Wm-8h: iscontinuouslyrotated at a constantspeed by anysuitable means? providedrior that purpose. The-shaft, I84mam. 752

591 v 'Ihezelectsomagnets for; instance; bhidvfileiiibyl a small:motion," or: a: plurality oiasuchzshaftszzasssnciaiediwitln aaplunaleitw'ofrswitohessmayshezgeaneditmwcommonmotmr driven shaft; Suuir."arrangements fbn' driving:

, switches: of theipnwen operated are well:

lmnwn; and: accordingly areznot shown herein.

From: the; foregoing it. will; be understood; that thesmllen Ififliisac'ontinuously: rotated; at -thei-desited? speed! by: the shaft I6 Themtafiom of roller Ifllfiis normallyeineflective; how even for itisxndrnralltmut: of engagement with bothof the rollers; lfllian'di I 52;being maintaihed in a central position by means off springs IE8 and I58which arlez attached to the= armature I512, 'IZo guard i againstaccidental moveme ntfiof thearmature-1 59K on itsipi'votsby shocla' orother cause; suchas might; bning'aboutta momentary engagement between.roller' E59! and} roller I5I or: roller F3225 light auxiliary:armatureflflfl may Be provided; This armature is: pivoted on: the maiirarmature I511? and: is: normally maintainedi at 1 right angles theretmbya spring: I IB whereby the-*endswfithe awgiliamr armature are adapted;to engagethe enclsi of" the brackets I65; and IE5 'and positivelyprevent any: undes-itahle movement of tlie=- mainarmature on its-pivot-vWham the electromagnet' I535 is: energized; the pole piece I553 firstoper ativelyz'attracts fiiaad acentend of the auxiliary armature I12which is thus rendered ineffective toapmeventithezmovement of the-mainarmature- IM? towardlthe pUIQpiQCBZ Theoperation' ofithemainiarmaturerhy electromagnet I53' brings roller I53 engagement-with roller: IEI Iand thereby causes the: notation of share M 05 a: simiiar manner: theenergization of electromagnet- W54 causesztherotationiof shaftlLI Ihybrihgi'ng roller I 58 into engagementiwithwollen I52.

'Ilhe bracket IIiEsnotoni y act's-:as-a stopsin ooomiiz ation. with?the: auxiliary: amnature I 12: but. eflsoaserves. to support a1 pairofcontact sphings I85: and: These Contact springs: arenormallyiimengagemeutbut areiseparated by alinolii oiiinsulatingmraltenia'llflflrwhenever thearmatiire; I51 is operated by the electromagnet I53..AI-sim- 1 ilatrset; of contact: p ings 3& an'di lam ssupported onebracketliliIiiv These springs-also: are normally closed; and areseparated: by: knob III whenever: the armaturea I61F"is:operated by:e1'ec-- tromagnet I54:-

means; I mzareibrake-ma'gfie nets; ailfil arez'pmvidedi with armaturesI803 and I?8:I; which ane adazpteil toLengagwtherollers I524 andi I5 I,respectivelyptovpnevent. rotation there:- ofi, as: willibezsubsequently; expiained mo'neain: de- Thee'magmets; H53 and". H215 are?mounted: on the frame plate lifidiby'mcam oflhrackets: Iiifliandi lfiarespectivslyi. 1

Riel-carriages Islitis normally. maintained: in: itsextremeipesitibn to:the left, ,whereritbears against.-

thexframei piate IUI,v,by*a clocksprin'gz lfiiLwhich:

ten'dsstozrotatethessha fttflminia' clockwise dime tifll'l' as". viewed;from: the: night: hand; ends of the: shaftiinfi'ig. 7. Aisimilarclocktspn n'gl I91 tends: to rotate the shaft III in the? same;direction;-

:1 whichzmaintainsathe kllbckcI imin: aaposition where it. bears;against. the. torn of. the GaJ'KIlKEELIIIQH pair'of: 01fnorma-lxspring's; comprisingithe comtact spnihge I85 andsl BS,.arenormallyimaiirtm'nedi open: by: the blocks IzIfll These springs; mayhe;

mounted; om the frame.- plate NH as shown; in;

' Fig. 7.

' Reference: now." be made, to: the: circuit dnawing;.Eig-: 12; which;shows the elentricaiicone neetionszof thersystemu The" reference:character- A. indicates: a. tale:-

inclusive.

phone, which'may beof any suitable common battery type. The conductors20D and EDI extend from the telephone'to'a terminal strip 2i34,where theconductors 262 and 203 coming from thecalling device CD are alsoterminated. At this terminal strip conductor 236,. is connected directlytats-in a clockwise direction from power supation releasesthe gear43,which starts to ro plied-by spring [6 and under the control of the tothelineconductor 265, while conductor 26! is I explained shortly.

- The switch S may have access to ten lines, one of which is shown, andcomprises the'line conductors 221 and 228. These conductors may extendto a telephone station B, which maybe a common batterytelephone similarto the tclephone A. The relays 229 to 223, inclusive, are at theexchange and are individual to the line of station B.

The functions of these relays will be governor 21.. When the key reachesits fully operatediposition, the shaft I4 is restored by spring 45, andthe key becomes lockedby bar 30, as shown in .Fig. 2. The .operation'ofthe key per- -mits contact spring 4! to engage contact spring 42,thereby, connecting contact 6| to the conductor 203.

Whenthe gear 43 isreleased as described-in thejforegoing,itmakes onecomplete rotation and then becomes. lockedin normal position, the

operated-key -1qbeing' released just before the gear=wheelfhas fullyreturned to normal. The

manner in-which these operations take place willbe readily understoodfrom the drawings,

particularly Fig. 5. Whenthe gear wheel ap A suitable source of currentis provided for operating the switch, such .as a storage battery, forexample. In theicircuit drawing connections to the negative pole of thebattery are indicated by arrows accompanied by negative signs, while'connectionsto the positive or grounded pole of the battery areindicated by the usual ground symbols. I i The operation of the systemwill now be 'described, it being assumed for this purpose that a call isto be made from, the station A to the station B. The line of stationB isconnected tothe first set of bank contacts in the switch S and'accordingly is selected by calling the digit v1.

When the receiver is removed at station A, a circuit is completedfor'the line relay 2! I, said c'onductor206, conductor 263, contact 1 l,brushes 24 and 25, ring 12, conductor 262, conductor 26!,

telephone at station A, conductor 206, line conductor 265,contactscontrolled at 230, an dthe upper winding of relay 2!! tonegative battery. Upon energizing, the line relay 2 closes a' circuitfor the slow-acting relay 212 at contact 232,

said circuit also including contact 243.. Upon energizing in turn, relay2!:2 prepares certain circuits at contacts 264 and 235, and at contact235'closes circuits for thebra-ke magnets H6 and ill. These circuitsinclude the sets of contact springs controlled by the armature I51 andwill be apparent upon inspection. The brake magnets energize when theircircuits are closed and their armatures grip the rollers I52 and 15!.

The calling party at station A may now operate the calling device keycorresponding tothe digit 1, rotating this key forward'from its normalposition as shown in Fig. 4 to the fully operated position in which itappears in Fig. 2. The operation of the key rotates the shaft l2 throughanangular distance of ninety degrees, and gear 13 and pinion l5 causeone full rotation of shaft l8, thereby winding spring I6. As the keyapproaches its fully operated position the hook 33 depresses the lockingbar 36, as shown in Fig. 5,

thereby rotating'shaft l4 and arm 56 and moving thehook 5'! far enoughtothe left sothat it can no longer holdthe pin 11.-

operpreaches normal position and shortly before: the

pin l1 reaches its dotted line position, the said .pin engages:the camsurface 58 on 'arm 56, whereuponthe further rotation of the gear wheelrotatesshaft l4 and depresses the lockingbar 30, This operation releasesthe operated 'key, which is :restored to normal position bythe spring40. ,As soon as the pin [.1 'passes'off the cam surface 58, the shaft [4is restored instantly,

the arm 56is moved to the right, and the pin l1 passes into the notchbehind hook 51. The gear wheel. 43 thusbecomes locked again, as showninFig. 4. After the keyhasl been released, reverse rotation of the shaft[2 and gear 1 I3 is prevented by the dog 59. The slight retrogrademovement that may occur before the .circuit extending from ground by wayof the v lower winding of the line relay, contact 23!, line i thirteen:equal spaces. occupiedby the-normal position contact H, 1 eavdogengagesa. tooth of gear [3 does no harm "because, of the ,fact that :thekeysmove through anarc. which is greater, than ninety degrees.

:During the rotation of the. gear wheel 43 the brushes 24 and 25cooperate with the commutator contacts to transmit two impulses over theline toeffect the desired control over the switch S, wherebythe saidswitch is caused to select the line of station B. These so-calledimpulses are actually interruptions of the. line circuit; When the brush24 leaves contact H the line circuit is opened, starting the firstimpulse. As the brush 24 engages contact 60, 69, etc., the line" circuitremains open, for these contacts correspond tothe tenth, ninth,-etc.,digit keys, which are in normal position. When brush 24; reachescontact" 6 I," however, corresponding to the first digit key, the-linecircuit isagain :closed, ,for contacts 4| and 42 have been closed bytheoperation of the key. The engagement'of brush 24 with contact i6lthus-terminates'the first impulse. The line. circuit is again openedwhen the brush 24-leaves contact 6], which thus startsthe secondimpulse... This impulse is ter- ;.mina te d Whenthe-brush 24reachescontact H,

where itcomes to rest. Whenthe-calling device is operated in accordancewith the digit 1, that is, when the first digit key is: operated, thetwo impulses result- 4 ing from the operation beara ratio to each otherwhich isasten is to one. Explaining this more in detaihthe path of thebrush 24 is divided into One of these I spaces is ing twelve spaces inwhich the line circuit may be"interru'pted when such-spaces aretraversed by brush 24.x Ten of these spaces are occupied by the'contacts6| to 60, inclusive, there being a bla'nlrspaceon either side of thecontact H.

These spaces correspond to time units, since the brush moves at constantspeed. Thus 'itwill'be energized.

.upward movement of the block MB.

ringing circuit closed for an interval after its circuit is broken.After relay 223 has deenergized the holding conductor 226 ismaintainedgrounded by way of contact 260 of relay 2'29 and contact 26I of relay22L .n 1

The grounding of the holding, conductor 226 completes a circuit forrelayZIIl, extending from ground on said'conductor. by waysof bankcontact 253, wiper I23, contact 239, and winding of relay 2H) tonegative battery. Upon energizing,-

relay 2H! disconnects the line relay 2 I} from line conductors 265 and206 at contacts controlled at 23!! and at contact 23L and at contact 230closes a local circuit for the line relay-including the resistance 2 35.The line relay 2II is thus held,

reaches the point X'i In response to the second "impulse theiblock I I8moves vertically during an intervalof seven time units and carriesthepin -I35 to the point Y. The wiper arm is rotated during the movement ofblock H8 and takes up a position alongthe line O--Y, therebypositionf-ingt'thewipers on the seventh'set of bank. contacts. rTheother digits'are called in the-same When the call is answered at stationB, the calling and called parties may carry on "a conversation in knownmanner, Current for the transmitter at station B is supplied through thewindby the replacement of the receiver at the calling station A. Whenthe receiver is replaced, the line circuit is interrupted and. the linerelay2i2fi is removing ground from the holding conductor 22B. Relay 2I0accordingly cleener gizes and breaks the circuit of the line relay 2 II. Upon deenergizing, the line relay, closes the previously describedcircuit including relay 2M and magnet I54, the said relay energizing anddisconnecting the switch wipers as beioreQ Magnet I54, upon energizing,brings rollers I58 and IEZinto'engagement and also opens contact springsI59 and IIE! to deenergize the brake magnet I'Iii. R'o-tationof shafts III and III now ensues, which raises the block I18 and pin I35 inthemannerv previously described. The movement of the block and pincontinues until the latter engages the rod I38, whereupon a circuit isclosed for relay 2H6, extending from thegrounded frame of the'switch byway of pin I35, rod Iii and winding of relay AIS to battery; Uponenergizing,relay 2 I5 locks itself at contactZM, and at contact 243 itbreaks the circuit of relay 2M and magnet I54 and also the circuits ofthe brake magnets H6 and I71.

The deenerglzafion of magnet dlsengages the? explained herein, whichhave been selected mereroller I55 from roller I52 and stops furtherenergization of the I brake magnets leaves the shafts I III and I I Ifree, with the result that they are rotated in the reverse direction bythe springs ISI and Hit. Thus the block H8 is lowered until way. Itmaybe stated generally thatthe impulse ratio is different for each digitand that when any digit is called the pin I35 of the switchis movedalong the two sides of a-right triangle in which thelengths of the sidesbear'the same ratio to each other asthe impulse ratio. The wiper arm isin any casepositioned along the hypotenuse of the triangle, a :linethe'slopeof which is deter- ;mined by the relative lengths of the sidesand not by their absolutelengths. j j

*It will be easily seen now why the speed ;of the calling device can bevaried independent of the switch drive speed without afiecting theaccuracy of selection. Suppose, for example, that the calling devicespeed increases, which will decrease the digit 7 is called the lengthofthe first imdeenergized, opening the circuitoi relay 22! and The deitagain rests on top of thecarriage H2, while i the latter is moved to theleftuntil it engages the fram plate MI. The wiper arm rotates. on

its pivot in response tothe movement of block I I8 and assumes ahorizontal position. i

response to the calling of other digits will be readily understood. Whenthe digit- .7 is called, for instance, by operation ofthedigit keycorresponding to the digit 7, the calling device CD transmits twoimpulses having an impulse ratio of four to sevn. In response tothefirst of these impulses the carriage I I2 moves to the right during aninterval of four time units and the pin I35 tively simple telephonesystem has been shown herein, the principle ofselection disclosed may beused in larger systems, following known meth- -odsi employed inexpanding the capacity of automatic telephone systems in common use. Itwill be understood also that thisnew principle of selection may beemployed ,to advantage in various other automatic switchingor indicatingsystems, and in suchcase the number. of selections or the number ofcalling device keys may be increased beyond the number shown herein. Noris the invention limitedto the precise impulse ratios*ly-asga'convenient illustration of the principle -involved. i i l,IQVarious other ;modifications may bennade :within the spirit of theinvention, and I do not therefore wish to berestricted'to the exact formof "the invention Which is shown and described herein, but. desire toinclude and have protected by Letters-Patentall forms and modificationsof my invention which come within the scope of the appended claims. i

Iclaim:

1.,Inan automatic telephone system, means forconnecting a calling andcalled line, comprising an automatic progressively movable switch,"means on the calling line for impressing two variable length but.continuous control conditions -on'the line for each number-called, theratio of Y 2. In an automatic telephone system, an; auto-:saidccontroller Ein .two stages, :the ratio :o'f' therdisnance iraveledEloy said controlleriin iOIIE :stage' to -the distancetraveledsintthaew'ther stageiheing :de-

:pendent on the :position zoiithercalledzlin'e termirnals "in :the bank.of said switch/and :a :progres- -:sively I, movable rbrushzcarriert'main'tained :in estation'ary position :during (the first stage :ofoperation I of .said controller and :advanced rover 1 said bank bylthecontroller in theesecond 'stage of its operation to select "the calledline.

3. In an automatic -=switching-isystem, a xifirst -line, a plurality: of'otherilines, :means Tfor closing the first '--line and for pro'ducin gtwo variable length interruptions therein,switching-means for selectingone (if said other lines, said switching -means including a controllermovable in two -di- \rections at right angles to eachother in responseto said interruptions, respectively, together with contactmean-spositioneii by=said oontroller, and

means for connecting said first 'line to ine sse- -'lected'-other lineresponsive to i the completion of the-selection.

ifiIn an *automatic switching system, a first "-line, a plurality ofother dines, -means for closing thefirst-lineanii'for producing twovariable "length-iriterruptions therein, an automatic-switch*-for-'selecting one fi -said other lines, aneansfor moving said switchto isel-ecting position in ac- -corn-lance with the *re'lative lengthsof said interruptions;and-meansfor connectingsaidfirstiline to thes'electedother line.

5. In an automatic switchingsyStemhamontrdl circuit, means forlosling*said'circuit, an auto- "matic switch,"means'responsive-to theclosure of ksaiii *circuit' for-preparing said switch for opera- "tion,means for producing two successive -interruptions -insa'id circuit,theiduration 10f isaidtinterruptions bearing-wpredetermined ratio to'each othergmeansfor operating 'said switch responsive to-saidinterruptions and'to 'an-extentdetermined "by-said ratimand means forreleasing said switch responsive to anot'her interruption :in saidcircult.

' 6. mm automatic-switching system; acontrol -circuit, an automaticswitch, means responsive to the' "closure of said circuit *for preparingsaid switch "for operation, -a-* positioning device inssai'd switch,means for continuously movingr 'saiil de vice in "two directions atright angles "to each cameraman -circuit, .means "for :imposing 7atcpntrol aconclition ion 'saidzoircuit, ;means :for :momentarilyinternipting said ricontrolacondition iat-ta'zvariahle'p oirit -betweenthe. beginning and ;end thereof, .a selecting mechanism, and meansion-operating said :mech'anism responsive 'to 1 said a'control conditionts a :po'sition de'te'rmin'e'd b the point rat which said interruptionoccurs.

210.111 -a control system, -a line, means for transmittingtwo impulsesover said line, including means for-varying therelative lengthsof saidimpulses at will, a controller moved in two 'di- ,-re'ctions at rightangles to'each'nther through "distances proportionate to the lengths ofsaid "impulses, respectively, and 'a responsive 'device including amember moved through an angle whose tangent is 'equal to "the -ratio ofone said,

' angles to-each otherin response to-said control .v conditions,respectively,=a secondnpartpivoted at .the'initial position .of saidfirst part, and -means for moving .said second part .on its "pivot to a,position defined'by the line which. is determined 7 I by the-initialand:final'positionsiof-said first part.

13.:In combination, a 'pivotedarm having :a ,plurality of selective,positions, reach-correspond- -ing to a difierent angularmovement ofsaid arm,

;means forzmoving said arm to-any' selective "posi- .tion, and means;fcr':controlling said 'moving mmeans-by a-pairof impulses ,of variableduration :such that 'thevra'tio of 'one impulse-to .thewother is equalto "the 'tangent of the angle :through :which arm liS moved to reach thexlesired :selective position. 1

F14. vIn comlzaination, "a switch zoomprising an arcuate ibank,a:pivoted:wiper arm carrying wip .-ers adapted :to lengageithe :contactsrot-said bank, -a;contro1ler normally located in alignment with thepivot of-said armand having a sliding con- 'other' in response to twosuccessiveinterruptions in "said circuit, *the final -position 0f saiddevice "depending on therela'tive-durationof said interruption-s,switching means in "said =swltch selectively controlled "by said deviceits 'final POSI- -tion, and means responsive toanotheri interrnption insaid circuit for restoring-said devicesanad said switching means. "7.nanautomaticslecting system, azline, a "controller, means responsive totwo' eontrolzconditions imposed cn'sa'id 'line for movingssaidcontroller along -the -two=s'i'des, respectively, of :amight'triangl'e,-and-a pivotedslectingsarmnaligned with the hypotenuse ofsaid tr'ian g'leibysaid-controller.

8. In an automatic selecting system, :a control --circuit,' means forimposing ea iCOIIbI'Ol condition omsaid' circuit, esai'd control.aconditionecomprising two parts o'f ivaria'lole :duration, sandselecting *mech-anism =-positienen iin :accordance with l-the 'ratio-bet-ween said parts and independent uof their sum.

cnection' with said arm, means for transmitting two impulses to 'saidswitch,--means-=responsiveto the first impulse for movingsaidcont-roller parallel to said arm, and means =responsive to thesecond impulse 'for *moving said controller at right-angles *to its'first direction "of movement,

thereby rotating-saidarm on its pivot.

15. In an automatic"telephone"system, callediiines, an automaticprogressively -movahle switch having access "to said lines, .a'callingiline 'ccnnected'to said switch for "controlling the same toextend connections'to certain of said "called lines in accordance withthe "digits of the 'callednnm- Tbersassi'gnecl thereto, means on "the'callingiline fliorimpressing two variable.calling'conditions on theline fcreach' digit of'the callednumoer "desired, saidconditions havinga predetermined ratio,-oneto the other, in accordance with the .digit,and meansin the switch operated responsive tosaidcal-ling conditionsofany digit to move '9. In an automatic selecting systermsa :c'ontrol j,75condition to the "other :and Lindependent of the duration of theconditions to select a particular one of said called lines.

16. In an automatic telephone system, a calling line, an automaticprogresive'ly movable switch controlled over said line, a plurality oflines accessible to said switch at different points in the movementthereof, means on the calling line for impressing a calling condition onsaid line for a predetermined time for operating said switch to seizeone of said lines, said means effective at will to divide the time ofsaid calling condition into two separate parts, the ratio of one part tothe other varying with diiferent' operations of said means, and meansfor operating said switch responsive to each calling condition to aparticular point to select one of said lines, the line selecteddepending upon the ratio of one-part ofnumber called, each pair ofimpulses having a predetermined ratio of duration one to the other for aparticular digit, and means in said switch operated in response to eachpair of impulses to select a particular one of said lines, the lineselected determined by the ratio of one impulse to the other.

' 18. In an automatic telephone system, a call- 7 ing line, an automaticswitch controlled over said line having a progressively movable wiperand contacts accessible thereto, means on the calling line fortransmitting pairs of impulses over said line representing differentdigits, each impulse of apalr having a definite ratio of duration to theether impulse of the pair, and said ratio differing for each digit,means in the switch responsive to a particular pair. of said impulses tomove said wiper in one continuous movement into engagement with aparticular one of said contacts,.the contact connected'with dependentionly on the ratio of one impulse of the pair to the other.

BERNARD D. WILLIS.

